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991.
We investigate a family of polytopes introduced by E.M. Feichtner, A. Postnikov and B. Sturmfels, which were named nestohedra. The vertices of these polytopes may intuitively be understood as constructions of hypergraphs. Limit cases in this family of polytopes are, on the one end, simplices, and, on the other end, permutohedra. In between, as notable members one finds associahedra and cyclohedra. The polytopes in this family are investigated here both as abstract polytopes and as realized in Euclidean spaces of all finite dimensions. The later realizations are inspired by J.D. Stasheff ?s and S. Shnider?s realizations of associahedra. In these realizations, passing from simplices to permutohedra, via associahedra, cyclohedra and other interesting polytopes, involves truncating vertices, edges and other faces. The results presented here reformulate, systematize and extend previously obtained results, and in particular those concerning polytopes based on constructions of graphs, which were introduced by M. Carr and S.L. Devadoss. 相似文献
992.
Tomáš Roubíček Giuseppe Tomassetti 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2010,61(1):1-20
Phase transformation in shape-memory alloys is known to cause electric resistivity variation that, under electric current, may conversely influence Joule heat production and thus eventually the martensitic transformation itself. A thermodynamically consistent general continuum-mechanical model at large strains is presented. In special cases, a proof of the existence of a weak solution is outlined, using a semidiscretization in time. 相似文献
993.
The aim of the present research work was to investigate the possibilities of designing surface texturing for different lubrication regimes and to evaluate its effectiveness, especially under starved, boundary and mixed lubrication regimes. This was achieved by combining an experimental tribological investigation with a surface-roughness analysis, a 2D FEM simulation and fluid dynamic modelling. The tribological investigation under unidirectional and reciprocating sliding was focused on the effect of the laser-texturing parameters—including the dimple depth and size, the dimple area density and the contact size—on the coefficient of friction under different lubrication regimes, achieved by varying the sliding speed, the normal load and the lubricant viscosity. 相似文献
994.
Horvat Alka J. M. Živko-Babić Jasenka Ivanković Danijela Babić Sandra Kaštelan-Macan Marija 《平面色谱法杂志一现代薄层色谱法》2001,14(6):426-429
JPC – Journal of Planar Chromatography – Modern TLC - Knowledge of the composition of an incorporated alloy is a precondition for avoiding polymetallism in subsequent prosthetic... 相似文献
995.
996.
Christopher Sørum Nebojša Simić Eirik Sundby Bård Helge Hoff 《Magnetic resonance in chemistry : MRC》2010,48(3):244-248
Chemical shift assignment of seven N‐substituted 6‐(4‐methoxyphenyl)‐7H‐pyrrolo[2, 3‐d]pyrimidin‐4‐amines, six of which are fluorinated, have been performed based on 1H, 13C, 19F, and 2D COSY, HMBC and HSQC experiments. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
997.
998.
We present a device which modifies the heat-pipe oven in such a way that the molecular number density can be drastically reduced. The device is essentially a small chamber with an independent internal heater inserted into the center of the ordinary linear heat-pipe oven which, in turn, serves as a reservoir of the liquid metal. The advantage of the present design of superheating within the heat-pipe oven, where temperature differences of several hundreds degrees centigrade were obtained, is shown in the case of far blue wings of the first self-broadened potassium resonance lines. 相似文献
999.
V. Bužek 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1990,17(2):91-100
We study exactly solvable Dicke-like model describing a system of spatially distributed two-level atoms coupled to a single mode cavity field. We study the model in one excitation sub-space, when the field is supposed to be initially in the vacuum state and just one atom of the atomic sample is excited. We show that depending on the particular spatial distribution of atoms the system under consideration can exhibit super-radiation or subradiation. Moreover, we investigate the dynamics of the two-atom system interacting with the cavity field initially prepared in an arbitrary state. Co-operative effects are discussed in this case. 相似文献
1000.
E. Šimečková P. Čižek M. Finger J. John P. Malinský V. N. Pavlov 《Hyperfine Interactions》1990,59(1-4):185-188
The angular distribution of γ-radiation from the decay of239Np oriented at low temperatures in gadolinium host was investigated. The orientation parameters B2 and B4 were determined.
The attenuation factors for two long-living states in239Pu at 391.5 keV and 285.4 keV were calculated. From the anisotropies measured the multipole mixing ratios for 11 gamma-transitions
in239Pu were deduced. The results obtained support the assignment of spins of the levels at 492.2 keV and 391.6 keV as 3/2− and 7/2−, respectively. 相似文献